C-arm equipment is commonly implemented for purposes such as surgical planning, co-registration, image fusion, navigation, implant fitting, surgical validation, etc. During these procedures, it is frequently desirable to observe the patient from several different orientations and is often preferable to do so without the need to reposition the patient. C-arm systems have been developed to meet these needs and are now well known in the medical and surgical arts. C-arm systems can be small enough and mobile enough to be present in an operating or exam situation without requiring the physician or technician to repeatedly move and without requiring the patient to change positions to obtain a suitable image. As an example, a gap defined by the C-arm gantry allows the device to laterally access a patient such that patient images are obtainable without physically moving the patient.
An x-ray source and an x-ray detector are generally mounted on opposing ends of the C-arm gantry such that x-rays emitted by the source are incident on and detectable by the x-ray detector. The source and the detector are positioned such that when an object (e.g., a human extremity) is interposed therebetween and is irradiated with x-rays, the detector produces data representative of characteristics of the interposed object. The data produced is frequently displayed on a monitor or electronically stored.
The C-arm gantry defines an axis of rotation about which the source and detector are rotatable. By positioning this axis of rotation at or near an object, and by rotating the source and detector around the object in an orbital motion, images of the object taken at a plurality of different orientations can be obtained. These images can be combined to generate a comprehensive three-dimensional image of the object. The process of combining images to produce a comprehensive three-dimensional image is commonly performed with reconstructive software.
The term “redundancy” refers to the process of obtaining data that is representative of a single portion of an object from multiple different orientations. Increasing the degree of data redundancy correspondingly increases image quality by reducing artifacts. “Artifacts” are distortions in an image that may be generated, for example, by reconstructive software in response to insufficient input data. One problem with conventional C-arm systems is that the gap defined by the C-arm gantry limits the range of orbital motion of the x-ray source and the x-ray detector. This limitation on the range of orbital motion correspondingly limits the degree of data redundancy obtainable, and therefore also limits image quality by increasing artifacts.